Help me understand x and y components, sin cos, etc.

I'm really having difficulty understanding how to approach problems in my physics class due to 1. never having taken physics before, and 2. having a professor that I cannot understand (english is not his native language, and he speaks very soft/fast).

We're now doing tension in class, and I'm having trouble with the first problem :(

Given this diagram (block is at rest), what is the tension on the left string?

http://img178.imageshack.us/img178/1751/untitledje1.png [Broken]

The only thing I can come up with is that since acceleration is zero, then Sum of Forces (Fnet) = 0.

The book says something like tension in the x direction is Tcos(theta) and tension in the y direction is Tsin(theta).

What does that MEAN? Does that mean they are the x and y components? please help!!

Yes, they are the componenets of the force on the block due to the string (tension).

The force actually acts along the string, 50 deg from the horizontal, towards the wall. But since force is a vector, you can split it up into components to make things simpler. Draw a right triangle with base angles 50 and 90. The "force vector" will be the hypotenuse and the two sides will represent the components.

Try to express the condition of equilibrium [tex]\vec{F}_{net} = \vec{0}[/tex] in a graphical way. Further on, note that every vector has a x and y component. So, everything that applies for your vectors, applies for the components, too.

The block is not accelarating, which implies that the net force acting on it is zero. As I said earlier, force can be considered a vector, F = Fxi + Fyj. If the net force is zero, so must be it's components.

It's known that there is no accelaration along the y-axis (also along the x-axis), and then there's gravity acting downwards. Therefore,

Fy(string) + force due to gravity = 0 (i.e. the y-comp of the net force is zero)

Fy(string) + force due to gravity = 0 (i.e. the y-comp of the net force is zero)

Force due to gravity = 147N, I understand this.

But how do I get Fy(string) ?

Jesus I hate physics, does every university throw problems like these at students and offer no help after "lecture"? Maybe I should consider transferring. After all, I'm studying computer technology and will never be exposed to this material after this semester.

The "Trigonometry formula" says that if you take the ratio of the components (in a certain way), you end up with the tangent of the angle. In you're case, Tsin50/Tcos50 = tan50 - this is must be familiar to you from trigonometry. The second part says that the forces acting along the x-direction add to 0, and the third part says the same about the y-direction. Remember, the minus sign indicates that that particular force acts along negative x-direction, or y-direction as the case may be.